The Kinetics of Electromigration Damage in Copper Films Studied by Isothermal Resistance Change Analysis

ABSTRACTElectromigration damage is one of the primary causes of the failure of interconnects in VLSI circuits. In this work, the response of Cu films to electromigration stress has been studied by an isothermal electrical resistance method. Accurate temperature measurement and control of Cu stripes stressed at elevated temperatures and high current densities were accomplished by use of a thin film thermistor. The activation energy and current density exponent were measured for vacuum evaporated Cu films and the values that were obtained are 0.79±0.02eV and 3.6±0.2, respectively. Scanning electron micrographs of stripes that underwent electromigration damage showed many voids in the cathode region, hillocks in the anode region, and both voids and hillocks in the rest of the stripe. The activation energies of two aluminum stripes were also measured by the same method. An average value of 0.54±0.02eV was obtained.